Population Genomic Analysis of Introgression between Outcrossing and Selfing Plant Taxa

属于不同植物物种的个体通常无法相互交配以产生可育的种子。在这种情况下，物种彼此之间保持不同，并且不交换遗传物质。然而，某些物种（约占所有植物的20%），尽管它们的花和叶的形状非常不同，但它们能够交配并产生杂交后代，这些后代的形状介于它们的父母之间。如果这些杂交种能产生花粉和种子，它们又能与亲本交配。这样做的结果是，一个物种的遗传物质被转移到另一个物种身上，而杂交物种则充当了中间的中间人。物种之间有共享的遗传物质。被转移的遗传物质可能会影响接收物种的行为方式。例如，这可能意味着接受者可以比以前更好地忍受内涝或低温，因为它从其他物种那里获得了这些特性。因此，物种之间遗传物质的转移不仅可以消除物种之间的差异，还可以让它们适应新的环境条件，比如我们所期望的气候变化。目前我们知道有许多对植物物种可以相互交配产生杂交。我们不知道的是这些物种之间有多少遗传物质交换，以及这在进化中有多重要。这项研究的目的是找出在英国许多地方形成杂交品种的两种常见开花植物——水杨和木杨之间交换了多少遗传物质。为了做到这一点，我们将在从未杂交过的种群中研究这两个物种的遗传物质。通过比较这两个物种的DNA序列，我们将发现它们的遗传物质有何不同。然后，我们将在它们杂交过的地区，以及它们一起生长但尚未明显形成杂交的地区，对这两个物种的遗传物质进行排序。DNA序列信息将告诉我们物种之间是否交换了遗传物质，交换了多少，以及遗传物质在哪个方向转移。对于我们这个物种，我们认为基因会从水獭身上转移到木獭身上，因为水獭对传粉者更有吸引力，而且比木獭更容易与杂交品种交配。为了研究这种想法是否正确，我们将收集杂交后代和杂交区域的父母，并将它们抚养长大。通过观察杂交后代的基因组成，我们将发现哪位亲本是种子的父亲，从而确定它是否像我们预测的那样优先与水獭交配。我们获得的结果将第一次使我们对当今种群中杂交物种之间的遗传交换程度有一个定量的认识。这将告诉我们杂交物种共享遗传物质的程度，并使我们能够评估当今杂交在植物进化和适应中的重要性。它可能会从根本上改变我们对植物物种作为独立而独特的实体的本质的看法，并使我们对今天发生在我们周围的英国农村的重要进化过程有更大的了解。

Individuals belonging to different plant species are usually unable to mate with one another to produce fertile seed. In this situation the species remain distinct from one another and do not exchange genetic material. However certain pairs of species (some 20% of all plants), despite being very different in their flower and leaf shapes, are able to mate and produce hybrid offspring which are intermediate in form between their parents. If these hybrids can produce pollen and seed they can in turn mate with their parents. The outcome of this is that genetic material from one species is transferred to the other, with the hybrid acting as a go between. There is sharing of genetic material between the species. The genetic material that is transferred may affect the way the recipient species behaves. For instance it may mean that the recipient can tolerate waterlogging or low temperatures better that before because it has acquired these attributes from the other species. So transfer of genetic material between species may not only break down distinctions between species, it may also be very important in allowing them to adapt to new environmental conditions such as we expect under climate change. At present we know of many pairs of plant species which can mate with one another and produce hybrids. What we don't know is how much genetic material is exchanged between these species and how important this is in evolution. The aim of this research is to find out how much genetic material is exchanged between two common flowering plants, water avens and wood avens, which form hybrids in many places throughout Britain. In order to do this we will look at the genetic material of the two species in populations that have never hybridised. We will find out how the two species differ in their genetic material by comparing the sequences of their DNA. We will then sequence the genetic material of the two species in areas where they have hybridised, and in areas where they grow together but have not apparently formed hybrids. The DNA sequence information will tell us whether genetic material has been exchanged between the species, how much has been exchanged, and in which direction the genetic material is transferred. For our species we think that genes will be transferred from water avens to wood avens, because water avens is more attractive to pollinators and will mate more often with the hybrid than will wood avens. In order to investigate whether this idea is correct we will collect the offspring of hybrids and parents in hybrid zones, and grow them up. By looking at the genetic makeup of the hybrid's offspring we will find out which parent fathered the seed and therefore whether it has preferentially mated with water avens as we predict.The results we obtain will give us for the first time a quantitative idea of the extent of genetic exchange between hybridising species in present day populations. This will tell us the extent to which the hybridising species share their genetic material, and will allow us to assess the importance of present day hybridisation in the evolution and adaptation of plants. It may fundamentally change our ideas about the nature of plant species as discrete and distinct entities, and open our eyes to an important evolutionary process that is happening around us today in the British countryside.